Tone control



Dec. 18, 1934. J G, ACEVES 1,984,357

TONE CONTROL Filed June 4, 1930 INVENTOR kl 5M ,W K BY AT RN Patented Dec. 18, 1934 UNITED STATES TONE CONTROL Julius G. Aceves, New York, N. Y., assignor, by mesne assignments, to Louis Gerard Pacent,

New York, N. Y.

Application June 4, 1930, Serial No. 459,246

10 Claims.

This invention relates to what is known as tone contro in the recording and reproducing of sounds.

Special objects of the invention are to reinforce certain desirable frequencies which under ordinary circumstances are more or less lost and to subdue other undesirable frequencies.

In particular, the invention aims to effect reinforcement of the bass tones in the range below cycles per second, to reinforce the treble tones above 1000 cycles per second, to eliminate the socalled scratch or surface noise and to reduce or eliminate the effect of resonant frequencies in the electrical and mechanical chain.

The foregoing and other desirable objects are attained in this invention by the novel circuit arrangements and other special features hereinafter disclosed and broadly covered in the claims following.

The drawing accompanying and forming part of the specification illustrates in a diagrammatic way one practical embodiment of the invention, but it should be understood that the actual structure may be modified as regards this disclosure all within the intended broad scope of the invention.

In the diagram, the input terminals are shown at the left and it will be understood that these are suitably connected with the circuit which is to be controlled, such for instance, as the circuit of an electric phonograph pickup, the output of a photo-cell amplifier orthe like.

One side of the input, that is the upper side 1 in the illustration is branched and one of these branches, the one designated 2 in the diagram is designed to favor the lower frequencies, while the other, that is the branch 3 is designed to favor the high frequencies. These have been descriptively called a bass booster and a treble booster. The first includes a condenser 4 and inductance 5 connected in series across the line and with the inductance shunted by a variable resistance 6. The so-called treble booster is shown as made up of a condenser 7 in series with a resistance 8 across the line, which resistance has a variable shunt circuit 9 including the pri mary 10 of a transformer 11, whose secondary 12 is connected in series relation with the other booster at one side and at the other side through battery 13 to the grid or input side of the amplifying tube 14.

The values of the bass reinforcing branch are selected to transmit high and intermediate frequencies without increase in the degree of voltage amplification and to transmit low frequencies with increase in the degree of voltage amplification, while the values in the other branch are selected to transmit substantially all the high frequencies with increase in voltage amplification. The outputs of these selecting branches, by being connected in series relation feed directly into the amplifying tube, so that with this simple arrangement, the desirable lower frequencies are brought out and at the same time the treble or higher frequencies are saved. The extent of reinforcement or amplification of these particular frequencies may be regulated by adjustment of the variable resistance 6 in the bass reinforcement branch and the variable resistance 8 in the treble reinforcement branch.

Thus the amount of gain or reinforcement of both the bass and upper register may be adequately controlled. As a further measure, the leakage inductance and the distributed capacity of the secondary in the transformer llmay, by suitable transformer design be made to reinforce the upper register.

The means for reducing objectionable speaker resonance and for suppressing the surface noise are directly associated in the present disclosure with the output of the amplifying tube and such means comprise in the present instance, sharply tuned resonant circuits.

In the illustration, a parallel feed path is connected across the output of the tube, including an inductance 15 in series with the plate potential source 16. The so-called speaker resonance suppressor is shown as consisting of a variable resistance 1'7, the variable inductance 18 and condenser 19, in series relation across the output circuit and the surface noise suppressor is shown as a variable inductance 20 and condenser 21 in series across the line, parallel with the resonance suppressor.

As the majority of record scratch is found to be located in the vicinity of 3800 cycles, the eliminator circuit 20, 21, is tuned to this frequency and therefore shunts out the record scratch or surface noise. The speaker resonance circuit is tuned to the resonance frequency of the speaker and its associated chain and when the two 'circuits' last described are properly adjusted, they may require no further attention from the operator.

Additional means for reinforcing certain of the base frequencies may be provided, if desired, the same being shown in the illustration as a circuit of the parallel resonance type, consisting of an inductance 22 and condenser 23 in parallel across the line with a variable resistance 24 in series, for quantitative adjustment. Once properly set, this circuit may not require further adjustment by the operator.

The output from the control system described may be passed directly into the first stage of an amplifier, under control of a fader 25.

The arrangement and combination disclosed enable the resonance of the natural periods of different speakers and auditoriums to be corrected for as needed. Also with this combination, the desired reinforcementor attenuation of selected frequencies may be determined at will. The structure is relatively simple and may be efficient- 1y combined with existing forms of apparatus.

What is claimed is:

1. A system for selectively reinforcing different frequencies of asignal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that the circuit is resonant at a predetermined low frequency, and a third circuit comprising in series the transformer secondary and the inductance of said second circuit.

2. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that the circuit is resonant at a predetermined low frequency, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, and resistances in said first and second circuits for controlling the degree of reinforcement effected by said circuits.

3. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that thecircuit is resonant at a predetermined low frequency, a

third circuit comprising in series the transformer secondary and the inductance of said second circuit, and an electron discharge device having its input electrodes connected to said third circuit.

4. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that the circuit is resonant at a predetermined low frequency, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, an electron discharge device having its input electrodes connected to said third circuit, and resistances in said first and second circuits for controlling the degree of reinforcement effected by said circuits.

5. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary, a second circuit comprising series connected capacitance and inductance, and. a third circuit comprising in series the transformer secondary and the inductance of said second circuit.

6. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary, a second circuit comprising series connected capacitance and inductance, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, and resistances in said first and second circuits for controlling the degree of reinforcement effected by said circuits.

7. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary, a second circuit comprising series connected capacitance and inductance, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, and an electron discharge device having its input electrodes connected to said third circuit.

8. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary, a second circuit comprising series connected capacitance and inductance, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, an electron discharge device having its input electrodes connected to said third circuit, and resistances in said circuits for controlling the degree of reinforcement effected by said circuits.

9. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that the circuit is resonant at a predetermined low frequency, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, a variable resistance in shunt to the transformer primary, and a variable resistance in shunt to the inductance of the second circuit.

10. A system for selectively reinforcing different frequencies of a signal comprising a pair of parallel circuits, the first circuit comprising series connected capacitance and a transformer primary having constants such that the impedance of the circuit to frequencies above a predetermined. value approaches the impedance of the transformer primary alone, the second circuit comprising series connected capacitance and inductance having constants such that the circuit is resonant at a predetermined low frequency, a third circuit comprising in series the transformer secondary and the inductance of said second circuit, an electron discharge device having its input electrodes connected to said third circuit, and an output circuit for said electron discharge device containing impedance comprising inductance and capacitance in parallel series relation with the resistance.

JULIUS G. ACEV'ES. 

